Drilling apparatus and adaptor assembly for such apparatus

ABSTRACT

The invention relates to drilling apparatus having an inner drill string and a surrounding outer drill string, which strings can be advanced simultaneously. Instead of these strings being rigidly coupled for simultaneous advance under a rotary percussive action, the inner drill string is connected to a first adaptor which is slidable but non-rotatable in a second adaptor to which the outer drill string is connected so that when the first adaptor is rotatively and percussively driven, the second adaptor and its associated outer drill string are rotatively driven. Percussion is preferably transmitted to the bit of the outer drill string by arranging the bit of the inner string to strike the outer bit, but alternatively or additionally the first adaptor may hammer the second adaptor.

Bray

DRILLING APPARATUS AND ADAPTOR ASSEMBLY FOR SUCH APPARATUS [76] Inventor: Richard Nicholas Bray, Farthings,

Restwell Ave., Cranleigh, England [22] Filed: Feb. 22, 1973 [21] App]. No.: 334,609

[30] Foreign Application Priority Data Feb. 25, 1972 Great Britain 8846/72 [52 U.S. Cl. 1 75/l 73, 175/257 51] ..E21 b5 0 0 [58] Field of Search...,.. ..17/ 1 7 3, 257, 321

[56] References Cited UNITED STATES PATENTS 984,825 2/1911 Ludlum 175/173 1,203,860 11/1916 Dunbar... 175/173 2,804,293 8/1957 Panks 175/214 3,000,453 9/1961 Germain. 175/173 3,005,504 10/1961 Mayhew, Jr. 175/173 3,227,230 l/1966 Lagerstrom 175/257 3,407,888 10/1968 Graipin .1 175/173 1 51 Sept. 17, 1974 3,682,260 8/1972 Klemm 175/257 Primary Examiner.lames A. Leppink Attorney, Agent, or Firm-Burns, Doane, Swecker & Mathis [57] ABSTRACT first adaptor is rotatively and percussively driven, the

second adaptor and its associated outer drill string are rotatively driven. Percussion is preferably transmitted to the bit of the outer drill string by arranging the bit of the inner string to strike the outer bit, but alternatively or additionally the first adaptor may hammer the second adaptor.

8 Claims, 5 Drawing Figures PMENTEB SEP] 7 I974 sum 10$ 3 DRILLING APPARATUS AND ADAPTOR ASSEMBLY FOR SUCH APPARATUS The present invention relates to drilling apparatus and to an adaptor arrangement for such drilling apparatus.

The type of drilling apparatus to which the present invention relates has inner and outer drill strings, the inner string comprising a rod assembly having a drilling bit at the lower end thereof and the outer string comprising a casing assembly surrounding the rod assembly and also having a drill bit at the lower end thereof.

When it is desired to drill through rock which iscovered by overburden, that is loose material such as earth, the inner and outer strings are advanced together through the earth and also for a short distance into the rock. Thereafter, the inner string is advanced alone through the rock and the outer string remains stationary and acts as a protective casing to prevent the'overburden from exerting pressure on the rod assembly.

One known design of such apparatus further includes means by whichthe two drill strings are coupled together for simultaneous rotary percussive movement. A shank adaptor is secured to a rotary percussive power source, the adaptor having at its lower end an internally threaded bore into which the rod assembly is screwed. The lower portion of the shank adaptor is externally screw threaded, and a sleeve-like casing adaptor has its upper end screwed onto such lower portion of the shank adaptor. The lower portion of the casing adaptor extends below the shank adaptor and is internally threaded to receive the uppermost section of the casing assembly. By means of the shank adaptor and easing adaptor the two drill strings are thus rigidly coupled together for simultaneous rotary percussive movement.

A flushing head is secured above the casing adaptor to the shank adaptor, the flushing head being rotatably connected to the shank adaptor so that the flushing head may remain stationary whilst the shank adaptor rotates. The flushing head serves to supply a flushing medium to the space between the inner and outer strings, and in order for the medium to reach such space, the shank adaptor is provided internally with axially extending channels which extend from the region of the flushing head to the base of the adaptor. As is customary, the shank adaptor also has a central axial channel extending the entire length thereof in order to transmit flushing medium along the adaptor to a central channel which extends the length of the rod assembly whereby flushing medium may leave the assembly in the region of the inner drill bit.

When, as described above, it is desired to advance the inner drill string only, the two adaptors must be uncoupled and the shank adaptor lifted to permit further rods to be added to the rod assembly. In order to uncouple the adaptors it is necessary to perform an unscrewing operation, and this is time consuming. Also, since the flushing head is secured directly to the rotatively and percussively driven shank adaptor, the bearing arrangement of the flushing head is subject'to a high degree of wear. Further disadvantages of the arrangement are that the shank adaptor is relatively expensive to produce because of the need to provide it with three channels instead of the customary single central channel, and the provision of channels near the outer portion of the shank adaptor may tend to weaken the same.

A preferred embodiment of the present invention may overcome or reduce all or some ofithe above mentioned disadvantages. I A

According to the present invention there is provided an adaptor assembly for drilling apparatus, the arrangement comprising a first adaptor which isto be connected to an inner drill string and a second adaptor which is to be connected to an outer drill string, the adaptors being constructed so that the second adaptor can receive the first adaptor in a bore in the second adaptor in such a way that the adaptors are coupled for simultaneous rotation but are axially slidable relative to one another.

In order to ensure simultaneous rotation of the two adaptors, it is preferable to make the first (i.e. shank) adaptor a close sliding fit within the second (i.e. casing) adaptor and to construct the first adaptor and its corresponding bore in the second adaptor to have a noncircular cross-section.

With an arrangement as described above in which the adaptors are not secured together, the first adaptor may be lifted from within the second adaptor without the need to unscrew any couplings.

Since the adaptors according to the invention are not rigidly coupled together, when the adaptors are in use on drilling apparatus, it is necessary to make provision for the transmission of percussion to the drilling bit of the outer drill string. This may be achieved by arranging for the first adaptor to strike the second adaptor by means of suitably co-operating shoulders on the adaptors. However, this has the disadvantage of stressing the outer string and the adaptors, and for this reason it may be preferable to use an arrangement in which percussion is transmitted direct to the drill bit of the outer string. Thus, the inner drill bit may be arranged to strike the outer drill bit in any suitable way, and preferably co-operating shoulders are provided on the two bits. With-such a system, percussion is transmitted from the first adaptor via the inner drill string and its drill bit to the drill bit of the outer casing, which latter drill bit may be connected to the outer casing so as to have axial play. As an alternative arrangement, the drill bit of the outer string could be integral with the lowermost section of outer casing. It is also possible for percussion to be transmitted to the outer bit by a combination of the two methods described above so that the adaptors and also the bits hammer one another.

Preferably the second adaptor has an upper portion in which the shank adaptor fits, and a lower portion below said upper portion and provided with apertures through which flushing medium may be supplied to the space between the inner and outer strings. With such latter arrangement, a flushing head may be secured to the casing adaptor instead of the shank adaptor, and it is thus not necessary to provide the shank adaptor with axially extending channels for the passage of flushing medium to the space between the outer and inner strings. Thus a cheaper and stronger shankadaptor may be provided.

Since the second adaptor is preferably not hammered directly, the bearing arrangement of a flushing head secured around the apertured region of the second adaptor may not be subjected to the same degree of wear as in the case of the above described prior art.

In order that the present invention may be more readily understood, one embodiment of drilling apparatus and an adaptor arrangement according to the invention will now be described by way of example and with reference to the accompanying drawings in which:-

FIG. 1 is a vertical sectional view through the upper portion of drilling apparatus having inner and outer drill strings, the view showing one embodiment of a combination of shank adaptor and casing adaptor according to the invention, a flushing head being secured in position around the casing whereby a flushing medium may be forced from the flushing head through apertures in the casing adaptor and down between inner and outer drill strings,

FIG. 2 is a horizontal view from above, mainly in section, taken on the line 22 of FIG. 1, the view showing a seal substituted for the flushing head illustrated in FIG. 1,

FIG. 3 is a diagrammatic vertical sectional view on a reduced scale showing both inner and outer drill strings secured to the adaptors of FIG. 1, the view illustrating one manner in which the apparatus may be utilized,

FIG. 4 is a view similar to FIG. 3, and showing a second manner in which apparatus according to the invention may be utilized, and

FIG. 5 is a view similar to FIGS. 3 and 4 and showing a third manner in which drilling apparatus according to the invention may be utilized.

FIG. 1 shows a shank adaptor 1 which is to be driven rotatively and percussively by a power source which is not illustrated. The shank adaptor 1 is a sliding fit within the upper portion of a sleeve-like casing adaptor 2, and a seal is provided between the adaptors by means of a pair of ring-like seals 3 received in corresponding peripheral grooves in the shank adaptor.

The shank adaptor 1 and the corresponding bore in the casing adaptor in which the shank adaptor fits are of the same cross-section, being mainly circular but havine one or more flat surfaces so that the adaptors are not rotatable relative to one another and the shank adaptor may thus drive the casing adaptor in rotation.

As is customary, the shank adaptor 1 has a central bore 4 for the passage of a flushing medium, usually air, down through the inner drill string 5 (see FIGS. 3 to 5) the bore having an enlarged diameter lower portion which is screw threaded to receive the upper hollow rod of the inner drill string. The lower portion 2a of the casing adaptor is internally screw threaded to receive the uppermost casing section of the outer drill string 14, and the central region of the casing adaptor is provided with a pair of diametrically opposed flushing apertures 6 whereby a flushing medium, usually water, may be supplied through the apertures 6 and down between the inner and outer drill strings as illustrated in FIG. 4.

Surrounding the central region of the casing adaptor 2, in the views of FIGS. 1 and 4, is a detachable sleevelike flushing head 7 which is rotatably journalled on upper and lower bearing rings 8 and 9, the weight of the flushing head being carried on the lower bearing 9 which rests on a peripheral shoulder 10 of the casing adaptor. The flushing head 7 may thus be lifted from the casing adaptor when not required without the need to unscrew any couplings.

A conventional arrangement of scrapers and seals is provided between the flushing head and casing adaptor both above and below the flushing apertures 6, whereby to prevent leakage of water from an annular chamber 11 of the flushing head which surrounds the apertured region of the casing adaptor. Flushing water is supplied to the chamber 11 by way of an inlet 12 of the flushing head 7.

FIG. 4 illustrates the manner in which drilling is conducted when the detachable flushing head is in use as shown in FIG. 1. The shank adaptor l is driven rotatively and percussively, and thus a drill bit 13 of the inner string is also driven rotatively and percussively.

Rotation is transmitted to the outer string 14 and thus to a drill bit 15 of such outer string by means of the cooperating adaptors as described above and percussion is transmitted to the bit 15 by means of co-operating frusto-conical shoulders generally indicated at 16 on the two bits.

Flushing water supplibd to the chamber 11 through the inlet 12 passes in the direction of the dotted arrows around the annular chamber 11, through the apertures 6, down between the inner and outer strings, and out into the material, for example earth, which is being drilled. It will be appreciated that the seals 3 between the two adaptors prevent water from escaping from the space between the adaptors. The unbroken arrows in FIG. 4 illustrates the path of flushing air down the inner string and out into the material being drilled in conventional manner.

If the inner string 5 and inner drill bit 13 were to be removed, then the outer string alone could be advanced by means of rotation only, the percussive action being discontinued.

FIG. 3 illustrates a mode of drilling in which the flushing head 7 has been removed. As mentioned above, such head may be removed simply by sliding the same upwardly to remove it from its location around the casing adaptor, and thereafter the head may be removed from its position around the shank adaptor either by temporarily uncoupling such adaptor from the power source or by lifting the shank adaptor and temporarily uncoupling the adaptor from the uppermost rod of the inner string. With the flushing head removed, flushing air passes down the inner string and upwardly between the inner and outer strings to emerge through the apertures 6 as indicated by the arrows shown in unbroken lines. With this arrangement, the seals 3 are not essential to the working of the apparatus.

FIG. 2 illustrates a seal 17 substituted for the flushing head. The seal is in the form of a sleeve split longitudinally from top to bottom to provide a gap 18. On either side of the gap suitable lugs 19 and 20 are secured to the sleeve, and these two lugs may be pulled together or allowed to move apart upon rotation of a suitable bolt 21. The seal is provided with apertures 22 which in FIG. 2 are shown out of registry with the apertures 6 in the casing adaptor whereby such apertures 6 are sealed. Thus, when air flushing is performed in a manner similar to that illustrated in FIG. 3 but with the seal in position around the apertures, the air passes directly from the inner string into the surrounding material being drilled instead of passing upwardly between the strings and out through the apertures 6.

It will be understood that the bolt 21 may be slackened to allow the seal to be rotated to a position in which the apertures 22 are in registry with the apertures 6 of the casing adaptor, and in these circumstances drilling proceeds exactly as shown in FIG. 3 since the seal has no effect. The seal therefore is of particular use when it is desired to alternate between the type of flushing illustrated in FIG. 3, and the type of flushing in which the apertures 6 are closed and air passes directly from inner string into the material being drilled.

As described above, it is necessary in certain circumstances to advance the inner drill string alone. In order to achieve this using the apparatus described above, it is merely necessary to raise the shank adaptor complete with inner drill string, to then substitute a smaller drill bit 23 for the drill bit 13 at the bottom of the inner string, and to then continue drilling in the conventional way with the shank adaptor spaced above the casing and the drill bit 23 drilling into the rock or the like. It will be observed that the drill bit 23 is constructed to be sufficiently small to pass through the drill bit of the outer string whereby the outer string remains stationary as drilling progesses. During the use of the apparatus in the manner illustrated in FIG. 5 flushing occurs in a manner similar to that illustrated in FIG. 3, except that air can escape at the top of the outer string other than by passing through the apertures 6. FIG. 5 shows drilling in progress with the casing adaptor 2 removed. However, it is not necessary to remove the casing adaptor 2 sine it does not impede to any great extent the operation of the drilling apparatus in the manner illustrated in FIG. 5.

With the arrangement described above in which the two adaptors are not secured together, the shank adaptor 1 may merely be lifted from within the casing adaptor without the need to unscrew any couplings.

When drilling occurs in the manner illustrated in FIG. 4, the flushing head is to some extent protected from percussive vibration because vibration is transmitted to the flushing head via the relatively long path of the complete length of inner and outer strings.

Since, in FIG. 4, water enters the apparatus below the shank adaptor, the shank adaptor need not be provided with axial channels for the passage of water and such shank adaptor is thus relatively cheap to produce and comparatively strong.

If it is desired to lift the outer drill string by raising the shank adaptor, means must be provided for preventing the shank adaptor from withdrawing from the casing adaptor. Thus, the upper portion of the casing adaptor may be provided with four apertures arranged in two pairs, each pair serving to receive one prong of a two prong fork-member (not shown) which may be passed through the apertures. Two apertures, one from each pair, are shown at 24 in FIG. 1. The spacing between the pairs of apertures and thus the spacing between the two fork prongs will be slightly greater than the diameter of the upper portion la of the shank adaptor (see FIG. 11) so that the fork may be slid into position above a frusto-conical shoulder lb of the shank adaptor and with its prongs positioned one on either side of the upper portion la of the shank adaptor.

Thus, when the shank adaptor is raised, the shoulder lb will engage beneath the fork prongs which pass through the apertures in the casing adaptor, and further raising of the shank adaptor will cause the casings to be lifted.

I claim:

1. An adaptor assembly for use with drilling apparatus, the drilling apparatus including an outer drill string with an outer drill bit fixed at the drilling end thereof, an inner drill string disposed within said outer drill string and having an inner drill bit fixed at the drilling end thereof, and surface means for transmitting percussive forces from said inner drill bit to said outer drill bit, said adaptor assembly comprising:

a first adaptor having means for connecting one end thereof with said inner drill string and means for connecting another end thereof with rotary and percussive drive mechanism, and

a second adaptor having means for connecting one end thereof with said outer drill string and means at the other end thereof for slidably receiving and locating said first adaptor in rotary driving engagement exclusive of percussive drive engagement, such that percussive drive may be transmitted from the first adaptor to the outer drill bit by way of said surface means, independently of the second adaptor.

2. An adaptor assembly according to claim 1 wherein the means of said second adaptor for receiving said first adaptor comprises a bore; said bore and said first adaptor having non-circular cross-sections, with said first adaptor being receivable in the bore with a close sliding fit.

3. An adaptor assembly as claimed in claim 2, in which the said bore in the second adaptor is in an upper portion thereof, and in which the second adaptor has a lower portion provided with at least one aperture through which flushing medium may be supplied to the space between the inner and outer strings.

4. An adaptor assembly as claimed in claim 3, and including a flushing head for connection around the second adaptor to supply flushing medium to said at least one aperture, sealing means being provided between the adaptors to prevent undesired escape of such flushing medium between the adaptors.

5. An adaptor assembly as claimed in claim 3, and including a seal for connection around the second adaptor and being rotatable between a position in which said at least one aperture in the second adaptor is closed and a position in which said at least one aperture is open.

6. An adaptor assembly as claimed in claim 1, and including means which are operable selectively to prevent the first adaptor from being withdrawn from the second adaptor when it is desired to raise the second adaptor by raising the first adaptor.

7. Drilling apparatus comprising:

an outer drill string having an outer drill bit rigidly mounted at a drilling end thereof;

an inner drill string extending within said outer drill string and having an inner drill bit rigidly mounted at a drilling end thereof;

a first adaptor connected to a connecting end of said inner drill string;

means drivably connected to said first adaptor for rotatably and percussively driving said first adaptor and said inner drill string;

a second adaptor connected to a connecting end of said outer drill string; said second adaptor including means for slidably receiving and locating said first adaptor to couple said first and second adaptors for rotary drive exclusive of percussive drive; and force transmitting surface means located remotely from said second adaptor for transmitting percussive energy from said first adaptor to said outer drill bit.

8. Drilling apparatus according to claim 7 wherein said force-transmitting surface means comprises cooperating frusto conical shoulders on said inner and outer drill bits. 

1. An adaptor assembly for use with drilling apparatus, the drilling apparatus including an outer drill string with an outer drill bit fixed at the drilling end thereof, an inner drill string disposed within said outer drill string and having an inner drill bit fixed at the drilling end thereof, and surface means for transmitting percussive forces from said inner drill bit to said outer drill bit, said adaptor assembly comprising: a first adaptor having means for connecting one end thereof with said inner drill string and means for connecting another end thereof with rotary and percussive drive mechanism, and a second adaptor having means for connecting one end thereof with said outer drill string and means at the other end thereof for slidably receiving and locating said first adaptor in rotary driving engagement exclusive of percussive drive engagement, such that percussive drive may be transmitted from the first adaptor to the outer drill bit by way of said surface means, independently of the second adaptor.
 2. An adaptor assembly according to claim 1 wherein the means of said second adaptor for receiving said first adaptor comprises a bore; said bore and said first adaptor having non-circular cross-sections, with said first adaptor being receivable in the bore with a close sliding fit.
 3. An adaptor assembly as claimed in claim 2, in which the said bore in the second adaptor is in an upper portion thereof, and in which the second adaptor has a lower portion provided with at least one aperture through which flushing medium may be supplied to the space between the inner and outer strings.
 4. An adaptor assembly as claimed in claim 3, aNd including a flushing head for connection around the second adaptor to supply flushing medium to said at least one aperture, sealing means being provided between the adaptors to prevent undesired escape of such flushing medium between the adaptors.
 5. An adaptor assembly as claimed in claim 3, and including a seal for connection around the second adaptor and being rotatable between a position in which said at least one aperture in the second adaptor is closed and a position in which said at least one aperture is open.
 6. An adaptor assembly as claimed in claim 1, and including means which are operable selectively to prevent the first adaptor from being withdrawn from the second adaptor when it is desired to raise the second adaptor by raising the first adaptor.
 7. Drilling apparatus comprising: an outer drill string having an outer drill bit rigidly mounted at a drilling end thereof; an inner drill string extending within said outer drill string and having an inner drill bit rigidly mounted at a drilling end thereof; a first adaptor connected to a connecting end of said inner drill string; means drivably connected to said first adaptor for rotatably and percussively driving said first adaptor and said inner drill string; a second adaptor connected to a connecting end of said outer drill string; said second adaptor including means for slidably receiving and locating said first adaptor to couple said first and second adaptors for rotary drive exclusive of percussive drive; and force transmitting surface means located remotely from said second adaptor for transmitting percussive energy from said first adaptor to said outer drill bit.
 8. Drilling apparatus according to claim 7 wherein said force-transmitting surface means comprises cooperating frusto conical shoulders on said inner and outer drill bits. 